Allow customized relative PYTHONHOME

Summary:
This change allows a hard coded relative PYTHONHOME setting. So that
python can easily be packaged together with lldb.

The change includes:
1. Extend LLDB_RELOCATABLE_PYTHON to all platforms. It defaults to ON
for platforms other than Windows, to keep the behavior compatible.
2. Allows to customize LLDB_PYTHON_HOME. But still defaults to
PYTHON_HOME.
3. LLDB_PYTHON_HOME can be a path relative to liblldb. If it is
relative, we will resolve it before send it to Py_DecodeLocale.

Subscribers: mgorny, lldb-commits

Tags: #lldb

Differential Revision: https://reviews.llvm.org/D74727

1 files changed, 27 insertions, 5 deletions

diff --git a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
index 722af71..f046bcf 100644
--- a/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
+++ b/lldb/source/Plugins/ScriptInterpreter/Python/ScriptInterpreterPython.cpp
@@ -277,14 +277,36 @@ public:
 
 private:
   void InitializePythonHome() {
-#if defined(LLDB_PYTHON_HOME)
+#if LLDB_EMBED_PYTHON_HOME
 #if PY_MAJOR_VERSION >= 3
-    size_t size = 0;
-    static wchar_t *g_python_home = Py_DecodeLocale(LLDB_PYTHON_HOME, &size);
+    typedef const wchar_t* str_type;
 #else
-    static char g_python_home[] = LLDB_PYTHON_HOME;
+    typedef char* str_type;
 #endif
-    Py_SetPythonHome(g_python_home);
+    static str_type g_python_home = []() -> str_type {
+      const char *lldb_python_home = LLDB_PYTHON_HOME;
+      const char *absolute_python_home = nullptr;
+      llvm::SmallString<64> path;
+      if (llvm::sys::path::is_absolute(lldb_python_home)) {
+        absolute_python_home = lldb_python_home;
+      } else {
+        FileSpec spec = HostInfo::GetShlibDir();
+        if (!spec)
+          return nullptr;
+        spec.GetPath(path);
+        llvm::sys::path::append(path, lldb_python_home);
+        absolute_python_home = path.c_str();
+      }
+#if PY_MAJOR_VERSION >= 3
+      size_t size = 0;
+      return Py_DecodeLocale(absolute_python_home, &size);
+#else
+      return strdup(absolute_python_home);
+#endif
+    }();
+    if (g_python_home != nullptr) {
+      Py_SetPythonHome(g_python_home);
+    }
 #else
 #if defined(__APPLE__) && PY_MAJOR_VERSION == 2 && PY_MINOR_VERSION == 7
     // For Darwin, the only Python version supported is the one shipped in the